The present invention relates generally to the regulation of the pressure within a feed system such as a fuel supply system and more particularly to a fuel pressure regulator for maintaining the pressure at a fuel pump outlet at a preferred level relative to the ambient air pressure.
One conventional fuel supply system, for example as may be found in an automobile, employs a conduit or pipe leading from a fuel reservoir or fuel tank, passing through a fuel filter and an engine or electrically driven fuel pump, and by way of a further conduit to a float bowl or reservoir in the carburetor. Frequently, such carburetor reservoirs employ a float which maintains the level of fluid within that reservoir constant. In these constant head type fuel systems, the fuel pump may be of the diaphragm type and when the carburetor fuel chamber is filled, a float valve closes in the carburetor, creating a back pressure in the fuel pump chamber, so that the fuel pump diaphragm is no longer actuated to supply further fuel. This disabling of the fuel pump is typically due to the fact that the diaphragm is spring actuated in one direction and actuated in the other direction by an eccentric or cam type arrangement and when the carburetor float valve closes and the pressure increases within the fuel pump, the diaphragm is forced against the spring by that pressure with the pressure being sufficiently high to hold the spring in that position.
While such a float controlled or constant head fuel supply system is quite successful in many applications, diaphragm type constant pressure fuel supply systems have also been devised, for example, for stunt aircraft, where a conventional float supply system would not be satisfactory. Such a constant pressure fuel supply device would have an inlet coupled to a fuel pump and an outlet coupled to the carbureting device. The pressure regulator has a diaphragm actuated valve which blocks the fuel inlet so long as the fuel pressure within the regulator is sufficient to maintain a spring which urges the diaphragm in a direction opposite to that which it is urged by the fuel pressure compressed. If the fuel pressure drops sufficiently, the spring forces the diaphragm to move, opening the valve and allowing additional fuel into the regulator from the fuel pump, thus maintaining a constant fuel pressure at the regulator fuel outlet. Such a fuel pressure regulator controls the fuel pressure in the carburetor by selectively blocking or unblocking the fuel pump outlet, and either this system or the previously mentioned conventional float system may be plagued by leakage problems since when the fuel pump output is effectively disabled, relatively high fuel pressures exist within the system, making the probability of fuel leakage much greater.
The success of any carburetor design is dependent upon its fuel metering system and variations in the fuel supply pressure to that metering system will vary the metering system from optimum. Such variations may be simply due to atmospheric changes or changes in the elevation of the system or in the case of a float type supply, splashing and disruption of the desired level may occur either due to the system not being maintained in the proper attitude or due to acceleration of the system.